KRAS and lung adenocarcinoma: The principal modifications detected in cancer types characterized by frequent KRAS gene mutations predominantly involve the substitutions of guanine with adenine in codon 12 (c.35G>A, p.Gly12Asp) in pancreatic and colorectal adenocarcinomas and guanine with thymine (c.34G>T, p.Gly12Cys) in lung adenocarcinoma [46,47].